Buying XK8 Conv'

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Am considering buying an XK8 Convertible. Around the £40K mark. Does anyone have any advise eg; things to be aware of, extras to make sure it has etc.
Also, what kind of % discount to haggle for, prices seem to vary for very similar spec' cars. I went to a dealer today and they said a normal service costs about £350 is this right?

Any help would be much appreciated.

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Thanks Danny, I will look into the XKR but I think the prices are a bit too high and I would then have to sacrifice the mileage but I may be lucky. I was told that the standard Sat Nav was a bit small and covered the three dials in the middle of the dash. Do you think these are fair comments?

Cheers for your help.